The standard interferometric fiber optic gyroscope (IFOG) requires some mechanism for phase modulating in order to move the operating point of the interferometer onto the more sensitive points of the intensity versus phase curve, at which there is also sign differentiation. The standard method of imparting a biasing phase modulation to counter propagating light waves in an IFOG is to use an optical phase modulator, such as a lithium niobate electro-optic modulator or a fiber-stretching piezo modulator. Since both of these technologies are direct optical phase modulators, they operate in the optical path and can have unwanted side effects, such as residual intensity modulation, optical attenuation, wavelength dependent loss, and the like.